Japanese Patent Application Publication No, 2012-104550 describes a semiconductor device. This semiconductor device includes a semiconductor module, and a cooler configured to cool the semiconductor module. The semiconductor module includes a semiconductor element encapsulated in molded resin, and a heat sink plate exposed on a surface of the molded resin. The cooler includes a cooling plate located on the heat sink plate of the semiconductor module via thermal grease.
The semiconductor module is subject to temperature-dependent thermal expansion. Thus, a change in temperature of the semiconductor module causes a distance between the semiconductor module and the cooler to change, as a result of which the thermal grease located between them is pushed out or drawn in. When such a behavior of the thermal grease (a so-called pump-out effect) is exhibited, air is drawn inside the thermal grease, and a performance to cool the semiconductor module may thereby be reduced. In regard to this, the semiconductor device of Japanese Patent Application Publication No. 2012-104550 adjusts pressure inside the cooler to deform the cooling plate in accordance with thermal expansion of the semiconductor module.